An application programming interface (API) allows a developer to expose content or services to internal or external audiences. For example, to access data and services of a backend server, a user device makes requests using an API call and the desired data/services are provided in response. A typical API development process includes a design phase in which an API is defined, a test phase in which design features are tested, and a deployment phase in which the API is finalized and made available to users. It is often difficult for a developer to test the design of the API before the API is fully implemented. That is, the developer must first design the definition/specification of the API, then code its implementation before being able to manually deploy the API to a live server for testing. If the design of the API is discovered to be incorrect after testing, the developer must go back and not only modify the definition of the API, but must modify the implementation code. Discovery of the error earlier in the development would lead to a more efficient development process. Thus, there is a need for a more efficient API development and testing environment.